Wireless third generation (3G) communications systems are currently introducing technologies in order to become spectrally efficient and provide improved support for data services. These efforts have resulted in the development of the 3G1x-EVDV standard, an evolution of CDMA2000 from the 3GPP body of standards. Similarly, the universal mobile telecommunications system (UMTS) standard has introduced several advanced technologies as part of the high-speed downlink packet access (HSDPA) specification. An aspect in all of these technologies is to ensure any associated control information is carried in an efficient manner.
Currently in the HSDPA standard, every mobile communicating voice and/or data has a dedicated control and signaling channel established between the base station and the mobile on the downlink. This channel is referred to as the dedicated physical channel (DPCH) in the standard. FIG. 1 illustrates the frame structure for the downlink DPCH. As shown in FIG. 1, the downlink DPCH includes portions of a dedicated physical control channel (DPCCH) and a dedicated physical data channel (DPDCH). Specifically, the downlink DPCH for a user includes the downlink transmit power control (TPC) information, the transport format combination indicator (TFCI) information, and the pilot field of the DPCCH. With respect to the DPDCH, the downlink DPCH includes the voice data and higher layer signaling data. However, as will be appreciated, if a mobile user is only involved in data communication, and no voice communication, then the DPDCH fields in the downlink DPCH are mostly empty except for the higher layer signaling data called the dedicated transport channel (DCCH).
As discussed above, the downlink DPCH is a dedicated channel for the mobile user. Accordingly, each user involved in voice and/or data communication has a corresponding downlink DPCH assigned, and each assigned DPCH requires the use of a channelization code for transmission. However, the base station only has a limited number of channelization codes to devote to establishing downlink DPCHs. Consequently, as the demand for data services increases, and more users of the system conduct strictly data communication, an insufficient number of channelization codes will be available to handle the data communication.